Bonding technologies: Optically clear adhesive (OCA) (part 3 of 3)

What is optically clear adhesive (OCA) bonding?

Rigid-to-rigid vacuum OCA bonding is a cutting-edge technology that allows we to provide thinner bond lines and as a result, thinner overall stack-ups. OCA bonding employs the use of a dry film pressure-sensitive adhesive to adhere layers together. For adhering two rigid components, a vacuum chamber removes all air from the part and applies the components together with optimum optical clarity, without forming any bubbles. OCA can also be used to adhere a non-rigid component (such as an overlay) to a rigid component, in which case a roller carefully pushes out all of the air between the two layers.

Why choose optically clear adhesive (OCA) bonding?

The main advantage of this bonding technology is the thinner bond line. Whereas liquid optically clear adhesive (LOCA) bonding can achieve a bond line between .015” to .030”, OCA bonding can get even smaller, achieving a .005” to a .008” bond line. This bonding capability is well suited for thin components including cover glass, touchscreens, and frameless LCDs.

Another advantage of optically clear adhesive bonding is that no curing is needed. Whereas LOCA bonding requires curing the liquid adhesive, this isn’t necessary for OCA bonding because a sheet adhesive is used instead. Using a sheet adhesive also allows the OCA bonding to provide a tighter tolerance and as a result, a consistent and flat bond line.

While there are several benefits to using OCA bonding, it may not be suitable for all applications. Unlike with LOCA bonding, optically clear adhesive bonding results in a bonded adhesive that cannot be reworked, which can result in lower total manufacturing yields and less room for error.